In history, Prithviraj Chauhan was a loser irrespective of the deceitful tactic used by Ghori to defeat him. Its the winners who generally write history and not the losers. There is no guesses that this is the main reason why Prithviraj Raso is still questioned by many historians. Also historians being from winner's end might not like to agree that a brave and righteous king like PRC was defeated by wrong ways, thus the simple way for them is to tarnish the image of the loser to justify the victory.
But to agree that there was indeed a PRC/Sanyo love story during that era does requires a mere common sense, as it is agreed that there was a bad blood between PRC and Jaichand due to Prithvi/Sanyo elopement.